Minerals and Earth's Crust Composition

Earth's Crust Composition

• The Earth's crust is made of minerals and rocks
• Minerals are individual crystals of the same substance
• Rocks are combinations of different minerals

Mineral Criteria

• A mineral must be solid
• A mineral must occur naturally (not man-made)
• A mineral must be made of non-living material
• A mineral has a definite chemical formula
• A mineral has a crystal structure

Mineral Formation

• Mineral crystals form in two main ways:
  • From dissolved substances in liquids (like evaporation or hot water)
  • From cooling molten materials (magma or lava)

Minerals & Crystals from Magma & Lava

• "Extrusive" Cooling (Lava cools fast)
  • Minerals form from hot magma or cooling lava
  • Cooling produces crystals (minerals)
  • Crystal size depends on cooling time (faster cooling = smaller crystals)
• "Intrusive" Cooling (Magma cools slowly)
  • Magma cools slowly, producing large crystals

Mineral Crystal Size

• When hot material cools fast, crystals are small
• When hot material cools slowly, crystals are large
  • Granite has visible crystals due to slow cooling
  • Rhyolite has small crystals due to fast cooling

Minerals formed by Evaporation

• Minerals form when solutions or mixtures evaporate
• Evaporation leaves behind dissolved substances
• The longer the evaporation process, the larger the crystal
  • Salt (halite), gypsum, and calcite are examples from ocean water

What is a Mineral?

• A mineral is a naturally occurring, inorganic solid
• It has an ordered internal arrangement of atoms (crystalline structure)
• It has a definite (but not always fixed) chemical composition

Identifying Minerals

• Physical properties are used to identify minerals
• Properties include:
  • Luster (how light reflects off the surface)
    • Metallic or non-metallic
  • Streak (color of a mineral's powder)
  • Crystal Shape (specific geometric form)
  • Hardness (resistance to scratching; measured by the Mohs Scale)
  • Color (can be misleading, due to impurities)
  • Special Properties (magnetism, fluorescence, reactivity with acid)
  • Density (mass per unit volume)
  • Cleavage (how a mineral breaks along flat planes)
  • Fracture (how a mineral breaks along irregular surfaces)
• Optical properties – light transmission
  • Opaque (light doesn't pass through)
  • Translucent (light passes through but not an image)
  • Transparent (light and images pass through)

Hardness: The Mohs Scale

• Hardness measures resistance to scratching
• The Mohs scale ranks minerals 1 (softest) to 10 (hardest)
  • Common objects have hardness values

Mineral Classification (by chemical composition)

• Silicates (most common, containing Si and O)
• Oxides (containing O and a metal)
• Sulfates (containing S and O)
• Sulfides (containing S and a metal)
• Carbonates (containing CO3)
• Halides (containing a halogen element)
• Native Elements (composed of a single element)

This quiz explores the composition of the Earth's crust, detailing the properties of minerals and the formation of crystals. Understand the criteria that define minerals and the differences between extrusive and intrusive cooling processes. Test your knowledge on how minerals and crystals develop from both lava and magma.